The genes coding for the crystal proteins synthesized by Bacillus thuringiensis are notable because they are expressed at extraordinarily high levels but only during sporulation and the gene products are insecticidal. A total of three projects are planned to continue studies of crystal proteins. The first is to isolate and characterize the B. thuringiensis, B. subtilis and E. coli RNA polymerases that transcribe crystal protein genes; if novel sigma subunits are found associated with these enzymes, the genes coding for the sigma units will be cloned. The second project is to identify the domain(s) responsible for toxicity and/or host range in selected genes coding for Lepidopteran-specific and Lepidopteran-Dipteran specific crystal proteins by constructing chimeras of two genes and by site directed mutagenesis. The third project is to investigate the mechanisms regulating expression of two genes (a gene coding for a Lepidopteran-specific protein and another coding for a mosquitocidal protein) in recombinant strains of E. coli.